I use Synaptic which you can install with:
sudo apt-get install synaptic
If you click on Origins on the left side of the Synaptic Window, the PPAs that are currently installed on your system, as well as their sources are generated between the "Reload" tile, and the "Sections" button.
You can choose to view "All" at the same time, which generates a list in the box to the right, or browse each source independently to view which packages are included in each respective PPA. (As well as which version is installed, what the latest version available is, and a description of each package.)
As for whether or not the PPA is trusted seems to be based on the user. I tend to search around to determine how many complaints a particular PPA has, as well as reviews on compatibility; or whether or not the package has been added officially.
More information pertaining to repositories, as well as various labels given to them, can be found here:
And another question on AskUbuntu, offers a more colloquial explanation here:
Are PPA's safe to add to my system and what are some "red flags" to watch out for?